Telephonic signaling device



April-21, 1936. A. FRIEDLANDER 2,038,427

' I TELEPHONIC SIGNALING DEVICE I Filed Aug. 20, 1954 2 Sheets-Sheet lApril A. FRIEDLANDER ,0

TELEPHONIC SIGNAL LNG DEVICE Filed Aug. 20, 19 54 2 Sheets-Sheet 2Patented Apr. 21 1936 TELEPHONIC SIGNALING DEVICE Albert Friedlander,Gerardmer, France Application August 20 1934, Serial No. 740,658

In France August 26, 1933 1 Claim.

The present invention has for its object an improvement in telephonicsystems, permitting to warn a subscriber talking on the telephone withanother subscriber that a third person is calling his number. With theexisting system, when a subscriber is talking on the telephone withanother subscriber he cannot know that a third person is calling him andtrying to enter into communication with him. This often involves seriousdisadvantages. It is therefore of great interest to provide a deviceadapted to call the subscribers attention to the fact that someone iscalling his number on the telephone.

According to the present invention, I provide, at the telephonicinstallation of each subscriber, an acoustic or optical, signalingdevice, such for instance as a special bell, a lamp, etc., adapted to bebrought into action, when, in the course of a telephonic conversationwith another subscriber, a third person is trying to get intocommunication with the first mentioned subscriber.

According to a preferred embodiment, this signal can be transmittedthrough the ordinary telephonic line of the subscriber who is talking bymeans of a current of a suitable frequency, for instance a musicalfrequency capable of acting on the diaphragm of the telephonic receiverof said subscriber.

These, and other features, of the present in- .30 vention will resultfrom the following description.

Preferred embodiments of the present invention will be hereinafterdescribed with reference to the accompanying drawings, given merely byway of example, and in which:

Fig. l is a diagrammatical view of a telephonic exchange of the ordinarymanually operated type;

Fig. 2 is a diagrammatical view of the special call plug or key to beinserted according to the present invention;

Fig. 3 diagrammatically shows a portion of a multiple exchange of theordinary manual type;

Fig. 4 shows another portion of this exchange;

Fig. 5 shows the modification according to the present invention;

Fig. 6 shows a portion of an ordinary automatic exchange; and

Fig. 7 shows how this exchange is modified according to the presentinvention.

Adverting first to Figs. 1 and 2, I will explain 50 the application ofthe invention to a manual exchange of the simple type. In Fig. 1, I haveshown at l the two-wire plug that serves to establish the connectionbetween the exchange and subscriber A. I have shown at 4 the twowireplug that serves to establish the connection between the exchange andsubscriber B. 5 is the station of the operator and 6 is the call source.

I have shown at 2 the listening plug of the opera.- tor and at 3 theusual double call plug. The arrows indicate the directions of opening ofthe 5. various plugs or keys. The operation of such an exchange is wellknown for someone skilled in the art. In order to make it possible towarn a subscriber already in communication with another subscriber thata third person is trying 10 to enter into communication with him Iinsert, according to the present invention, in the exchange of Fig. 1, asource of alternating current of suitable frequency (for instance in thesimple case that consists in producing in the receiver of $15 thesubscriber to be warned a low buzzing, a musical frequency) and asupplementary special key permitting to send this current into thetelephonic line of this subscriber. This organ is shown by Fig. 2. Thisdevice is to be inserted be- 243 tween points a a and b b of Fig. 1. Ihave shown at l the source of alternating current of musical frequencyand at 8 a special double call plug. Supposing that subscribers A and Bare talking together, and that a third subscriber C .5 is trying toenter into communication with one of these two first mentionedsubscribers, it sufiices for the operator to move plug 8 either in thedirection of double arrow 9 (in order to warn B) or in the direction ofdouble arrow Ill (in order to 30 warn A) and then, eventually to signaloccupied to subscriber C, especially advising him that subscriber A or B(according to which of them is being called by C) has been warned.

In Figs. 3 to 5, I have shown the application 3-5 of the invention to amultiple manually operated exchange. In such an exchange there existseveral switchboards among which the subscribers are distributed. Ineach switchboard, there exist, on the one hand, holes corresponding 40to the group of the subscribers that are calling and on the other handholes corresponding to the group of subscribers that are to be called.In Fig.

3, I have shown at l l a subscriber line and at f3 a third wire (localwire) permitting the operator to ascertain, in the known manner whetherthe subscriber that is called is free. At I4, I have shown the jack of aboard corresponding to one of the subscribers of the group that can callthrough this board and at H and i8 jacks of either boards the number ofwhich is determined by the number of subscribers.

In Fig. 4, I have shown at 24, 25, 26 a plug with three conductors, thethree ends of which correspond respectively to conductors l5 and I6 55,

of line H, l2 and to ring [4 connected to Wire I3, when the plug isengaged in jack [4, l5, l6. In a likewise manner, plug 36, 31, 38corresponds to the jack of the subscriber that is called. Between thetwo plugs of the exchange there exists a known circuit some elements ofwhich, which are necessary for the good understanding of the operationof the device, have been shown in the drawings. Wires 42 and 43 areshown with a certain gap in which are inserted apparatus which are knownand have no bearing whatever on the present invention. Conductor 26 ofplug 24, 25, 26 is connected to the earth 3!] through'a relay 28 actingon circuit breakers 21 and 3! of line 42, 43 and through a battery 29. Ihave shown at 23 a relay through which wire I3 is connected to theearth. When plug 24, 25, 26 is inserted into a local jack (such as M,I5, [6) relay 28 is energized, same as relay 23, which is connected inseries with relay 28. Wire I3 is given a certain potential with respectto the earth, owing to the resistance of relay 23. This difference ofpotential is zero if the relay is not energized. Before establishing theconnection between A and B, the operator touches, through the end 38 ofplug 36, 31, 38, the ring of the jack of the subscriber B that iscalled. If relay 33, connected to the earth 35 through a battery 34 andacting on contacts 32 and H of line 42, 43, is not energized, wire 38 isconnected, through circuit breaker [8, with transformer 48 at theinstallation of the operator, which includes a receiver '39. If thesubscribers line is free, the test relay (corresponding to relay 23 ofsubscriber A) is open and no difference of potential exists in the localwire connected to the ring. The operator therefore establishes theconnection. On the contrary in the line of subscriber B is not free, itstest relay is energized and there exists a difference of potential whichproduces in receiver 39 a characteristic noise signaling that thetelephonic line in question is not free.

In Fig. 5 I have shown the auxiliary device according to the presentinvention, which is intended to warn a subscriber talking with anothersubscriber that someone is trying to get into communication with him.According to the invention, the arrangement concerning plug B ismodified as shown by Fig. 5. In this case also 36, 31, 38 are the threeconductors of the plug, 33 is the relay, 34 the battery, 35 the earth,32 the circuit breaker of line 42, I8 the circuit breaker of line 43 andthe listening receiver is shown at 39. I have shown at 52 a source ofalternating current of musical frequency and at 45, 46 a double keypermitting to warn either of the two subscribers A and B that someone istrying to get into telephonic connection with him. This device iscompleted by a key 5|, called occupation key, preventing relay 33 frombeing energized.

In Figs. 6 and 7, I have shown the application of the invention to animproved multiple exchange. In exchanges of this kind, the test nolonger exists and the diagram of the plugs is modified in such manner asto automatically prevent a double connection. In Fig. 6, I have shown aportion of the line of Fig. 3 and the modification of the diagram ofFig. 4 concerning plug B in the case of an automatic exchange. I3 is thelocal wire and I4, l1, and 20 the jack. Relay 23 is replaced by relay23a completed by a battery 53 inserted between the relay and the earth.In a likewise manner, relay 28 is replaced by a relay B comprisingwindings 55 and 51 in series, winding 51 having a high resistance. Whenonly plug B is engaged, battery 53 feeds current in series throughrelays 23a and the resistances 56 and 51. Relay B is caused to work andcloses switch 58, which short circuits resistance 51 the current flowingthrough 56 to the earth at 54. Winding 56 keeps switch 58 closed. Ifanother plug B1 is engaged in a hole, the current will not be any longersufficient for operating relay B1 mounted in shunt on the low resistance56.

In order to obtain the working of the supplementary signaling deviceaccording to the present invention the structure of plug B is modifiedas shown in Fig. '7. Relay B is not modified but resistance 51, insteadof being directly connected to the earth, is connected to one of theterminals of a more sensitive relay 60 the other terminal of which isconnected to the earth at 59. Relay 68 is capable of working under theaction of a small current and it is slightly retarded in such manner asto permit the special current to flow only when B shall not have actedowing to the telephonic line being not free. When relay 60 is broughtinto play, it closes contacts 62 in such manner as to send the specialcurrent supplied by source Bl to the subscriber that is called while heis talking with another subscriber. This current is also sent to theperson that is calling said subscriber. I

In a general manner, while, I have disclosed, in the embodiments abovedescribed, what I deem to be practical and efficient devices, it shouldbe well understood that I do not wish to be limited thereto as theremight be changes made in the arrangement, disposition and form of theparts without departing from the principle of the present invention ascomprehended within the scope of the appended claim.

What I claim is:

In combination, a telephonic system including a plurality of subscribersstations, telephonic lines leading to these stations, an exchange forconnecting these lines together, a signal at a subscribers station forwarning him, when he is talking with another subscriber, that he isbeing called by a third subscriber, a signal at said third subscribersstation, said exchange including a listening plug, the usual double callplug, a local source of current, a circuit including said source and aspecial double call plug for connecting said circuit with both of saidsignals through the telephonic lines of the corresponding subscribersstations.

- ALBERT FRIEDLANDER.

